Helically crimped filamentary materials

ABSTRACT

DISCLOSED IS A CRIMPED COMPOSITE FILAMENT HAVING A CRIMP INDEX IN THE RANGE OF 40% TO 70% AND 8 TO 25 CRIMPS PER INCH, SAID FILAMENT COMPOSED OF POLYETHYLENE TEREPHTHALATE POLYMERS HAVING DIFFERENT INTRINSIC VISCOSITIES AND HAVING VALUES OF BIREFRINGENCE WHICH DIFFER BY AN AMOUNT WHEREBY THE FACTOR $IV.$BR LIES IN THE RANGE OF 1.9X10**-4 TO 3.3X10**-3 WHERE $IV IS THE DIFFERENCE IN INTRINSIC VISCOSITIES AND $BR IS THE DIFFERENCE IN THE BIREFRINGENCE OF THE TWO COMPONENTS.

States 3,595,738 HELICALLY CRlMPED FILAMENTARY MATERIIALS Barry Henson Clarke and Geoffrey Marshall, Harrogate, England, assignors t Imperial Chemical industries Limited, London, England No Drawing. Filed May 21, 1968, Ser. No. 730,930 Claims priority, application Great Britain, May 22, 1967, 23,671/ 67 lint. Cl. DtlZg 3/02 US. Cl. 161-469 4 Claims ABSTRACT OF THE DHSCLGSURE The present invention relates to composite filaments which are highly suitable for use in stuffing or filling applications.

In the following description and claims, filament is used generically to denote continuous filaments or staplefibres unless it is obvious that continuous filaments or staple fibres are specifically intended from the text.

It is known that filaments possessing a three-dimensional crimp of the reversing helical type have advantages, when used as filling or stutfing materials, over filaments which have been crimped two-dimensionally by mechanical means. These advantages are that stuffing materials composed of helically crimped filaments exhibit greater bulk and are more resistant to, and have a greater recovery from, compression. However, it appears that these advantages are only apparent provided the scale of the helical crimp is within certain limits. Thus if the filaments have less than about 8 crimps per inch and a crimp index less than about 40%, the filling or stuffing material made therefrom has low resistance to compression. If, However, the filaments have more than about crimps per inch and a crimp index greater than about 70%, they are diflicult to separate by conventional textile techniques,

for example by carding, and the stuffing or filling material has low bulk and poor recovery from compression. The crimp index is calculated in accordance with the formula:

Crimp Index X 100 359,738 Patented July 27, 1971 An object of the present invention is to provide a filament which is highly desirable as a filling or stufling material.

According to the present invention, a composite filar ment possessing reversing helical crimp, characterised by a crimp index in the range of 40% to and 8 to 25 crimps per inch, comprises two synthetic polymers so distributed in the filament that it has along its length a cross section made up of two distinct components arranged eccentrically, each component consisting of one of said polymers, and the two polymers being polyethylene terephthalates having different intrinsic viscosities and having values of birefringence which differ by an amount whereby the factor AIVABR lies in the range 1.9 X10 to 3.3 10" where AIV is the difference in intrinsic viscosities and ABR is the difierence in birefringence of the two components. The intrinsic viscosity of each component, in deciliters per gram, is measured using orthochlorophenol as solvent at a temperature of 25 C.

For the optimum performance of the filament, for example of 4- denier per filament, as a filling or stuffing material it is preferred that the average number of crimps per inch is 13512.5.

The proportions of the polyethylene terephthalate components in the filament may vary between :20 and 20:80, but preferably the proportions are substantially equal.

The components of the filament may be arranged in a side-by-side structure in which each component forms part of the surface thereof. Alternatively, however, the components may be arranged in a sheath-core structure in which only the sheath contributes to the surface of the bicomponent filament.

When used as a stuffing or filling material in, for example, pillows and quilting, bicomponent filaments of the invention are formed into a non-woven structure which, according to another aspect of the present invention, has a specific volume when uncompressed of at least 80 cubic centimetres per gram and a specific volume of at least 30 cubic centimetres per gram when compressed under a load of 10 grams per square centimetre.

Bicomponent filaments of the present invention which are of particular interest are those which have values of the factor AIVABR lying in the ranges 2.9 l0 to 4.5 1O and 1.4x l0- to 2.1x 10 Filaments having AIV.ABR values in the range of 2.9 lO- to 4.5 l0 may be prepared from as-spun filaments having AIVABR values between about 9 X lO and 1.4 10" where ABR is the difference in birefringence of the components of the as-spun filaments, by drawing a tow of as-spun continuous bicomponent filaments in steam, relaxing the filaments by releasing the tension on the tow to develop spontaneous crimp, and enhancing the crimp by heat treating the relaxed filaments to develop potential crimp. Filaments of the invention having AIVABR values in the range 1.4x 10* to 2.1 x 10 may be prepared from as-spun filaments having AIVABR values between about 4.3 l0 and 6.6 l0 by using the crimping method described and claimed in copending United Kingdom application No. 23,672/ 67. This method comprises drawing a tow of as-spun bicomponent continuous filaments, relaxing the two while it contains at least 10% by weight of a liquid wetting agent to develop spontaneous crimp, and heat treating the relaxed filaments to develop the potential crimp.

The latter method is the preferred one because it enables filaments of the desired crimp properties to be obtained from filaments whose spinning requires less stringent control than those used in the former crimping method.

The invention will be further described by reference to the following examples.

EXAMPLE I Polyethylene terephthalate chip of intrinsic viscosity 0.675 decilitre per gram and polyethylene terephthalate chip of intrinsic viscosity 0.485 decilitre per gram were dried separately in an atmosphere of nitrogen at a temperature of 170 C. for four hours, after which they had intrinsic viscosities of 0.666 and 0.447 respectively. Each batch of dried chip was melted and fed through a screw extruder to the same spinneret pack maintained at a temperature of 283 C. wherein the two streams of molten polymer were combined just prior to extrusion. The spinneret had 300 holes, each 0.035 inch in diameter and its exit disposed on a bevel inclined at 60 to the axis of the hole. The bicomponent filaments extruded from the spinneret had the components thereof arranged in a sideby-side relationship and in substantially equal proportions. From the known characteristics of the melt spinning unit, it was estimated that in the spun filaments the components had intrinsic viscosities of 0.642 and 0.465 respectively.

The filaments were wound up at 3000 feet per minute and the rate of extrusion was adjusted so that the spun filaments had a denier of 14. Optical measurements revealed that the two halves of the spun filaments had birefringences of 2.23 X 10- and 5.43 li.e. a difference ABR of 3.2 l0 The factor AIVABR of the spun filaments had the value 61.6

A tow comprising 16,000 of the spun bicomponent filaments was passed through a bath of water containing 2.0% by weight of a textile finishing agent. The tow was then passed through a feed/draw rolls system, without slippage, and the draw rolls were rotated 3.9 times faster than the feed rolls so that the filaments were drawn by this amount. The tow of drawn filaments was maintained under a tension sufficient to keep the filaments straight, and was passed through a pair of rolls nipped lightly together. 'On leaving the nip rolls the tow contained 14% by weight of the liquid wetting agent.

The tow then passed into an air ejector, to the outlet of which was connected a flexible tube, and was conveyed to the brattice of a heat setting oven. Relaxation of the tow occurred within the fiexible tube as the tension on the tow was reduced and crimp was developed simultaneously in the filaments. As the fully relaxed tow was deposited on the brattice it was observed that the tow had split up into several sub-tows, each containing many filaments crimpted together in register.

The tow of crimped filaments was heat set in the oven at a temperature of 135 C. for ten minutes and was then cut into 2 inch stable fibres. The staple fibres had a reversing helical crimp with an average crimp index of 58% and an average number of crimps per inch of 15. The birefringences of the components of the heat set fibres were 0.159 and 0.169, that is a difference, ABR, of 0.010. The factor AIV-ABR of these fibres had the value EXAMPLE II Polyethylene terephthalate chip of intrinsic viscosity 0.675 decilitre per gram and polyethylene terephthalate chip of intrinsic viscosity 0.600 decilitre per gram were dried separately in an atmosphere of nitrogen at a temperature of 170 C. for four hours, after which they had intrinsic viscosities of 0.654 and 0.594 respectively. Each batch of dried chip was melted and fed through a screw extruder to the same spinneret pack maintained at a temperature of 283 C. wherein the two streams of molten 4 polymer were combined just prior to extrusion. The spinneret had 36 holes, each 0.015 inch in diameter and its exit disposed on a bevel inclined at 30 to the axis of the hole. The bicomponent filaments extruded from the spinneret had the components thereof arranged in a side-byside relationship and in substantially equal proportions. From the known characteristics of the melt spinning unit, it was estimated that in the spun filaments the components had intrinsic viscosities of 0.630 and 0.575 respectively.

The filaments were wound up at 4000 feet per minute and the rate of extrusion was adjusted so that the spun filaments had a denier of 11. Optical measurements revealed that the two halves of the spun filaments had birefringences of 4.3 X 10* and 6.8 X l0 i.e. a difference ABR of 2.5 10- The factor AIV-ABR of the spun filaments had the value 1.38 10 A tow comprising 12,600 of the spun bicomponent filaments was then subjected to a drawing operation during which the filaments were drawn 3.33 times their original length. The tow of filaments was maintained under sufiicient tension to keep the filaments straight, and was passed through a pair of rolls nipped lightly together. As the dry tow emerged from the nip rolls it entered an air ejector having a flexible tube at the outlet thereof. Relaxation of the tow and development of crimp occurred within the tube as the tension on the filaments was reduced. The relaxed tow was deposited onto the brattice of a heat: setting oven and it was observed that the filaments had crimped individually and not in register.

The crimpted tow was heat set in the oven at a temperature of C. for ten minutes, sprayed with a textile finishing agent, and then cut into 2 inch staple fibres. 'Ihe staple fibres had a reversing helical crimp with an average crimp index of 44% and an average number of crimps per inch of 14. The birefringences of the components of the heat set fibres were 0.144 and 0.152, giving a difference, ABR, of 0.008. The factor AlV-ABR of these fibres had the value 4.41 X 10 Samples of non-woven structures were prepared from the fibres of the invention by carding approximately 8 ounces of the fibres into a web 12 inches wide. The web was collected on a drum 18 inches in diameter, and was rolled during collection by a roller 12 inches long by 5 inches diameter and weighing 2.5 pounds.

The bulk properties of the web were measured using a modified Instron tensile tester. Pieces 7 inches square were cut from the web and were stacked to give a sample weighing between 15 and 30 grams. The sample was placed between a lower circular plate, A, 36 cms. diameter, and an upper circular plate, B, 11.3 cms. diameter, surrounded by an annular plate, C, having internal and external diameters 11.9 cms. and 36 cms. respectively. The sample Was compressed and allowed to recover by raising and lowering the first plate A, during which action plates B and C remained stationary and in the same plane. The annular plate C acted as a guard ring, and the load exerted on the plate B only was recorded. The sample was cycled ten times between loads corresponding to pressures of 0 and 10 grams per cmr On the eleventh cycle, the separation of plates A and B was recorded as a function of the load exerted on plate B. From these results and the weight of the sample can be calculated the specific volume of the sample, SV n, in cm. gm.* under various axial loads, n, in grams per cmr A table of results is given below of a comparison of the bulk properties of webs of fibres of the invention and webs of helically crimped fibres having crimp properties outside the range of the invention. The wet method denotes the production of the crimped fibres in which a liquid wetting agent was used, and the dry method denotes the production of the crimped fibres in which the liquid wetting agent was not used. Low values of SV indicate low resistance to compression, and low values of SV indicate low bulk and poor recovery from compression.

Average Average number C. 8V0, SV Sample No Method All .ABR of crimps percent em. gm. cm. gmr Performance 1 Wet 5.2 7 39 Fibre carding poor; low web 8 52 146 29 cohesion. Bulk: low resistance to compression. 10 48 135 30 12 50 117 45 13 55 115 42 l 14 44 112 41 O 2 15 58 103 45 U 17 54 101 41 18 47 97 40 23 59 91 43 27 61 73 40 Carding poor. 35 57 66 40 Low bulk; poor recovery.

1 Range of preferred bulk properties. 2 Range of satisfactory carding performance.

Samples 3 to 10 had the balance of desirable properties and were much superior to samples 1, 2, l1, and 12.

What we claim is:

1. A composite filament possessing reversing helical crimp, characterised by a crimp index in the range from 40% to 70% and 8 to 25 crimps per inch, comprises two synthetic polymers so distributed in the filament that it has along its length a cross-section made up of two distinct components arranged eccentrically, each component consisting of one of said polymers, and the two polymers being polyethylene terephthalates having different intrinsic viscosities and having values of birefringence which diifer by an amount whereby the factor AIV-ABR lies in the range 1.9)(10 to 3.3 10* where AIV is the difference in intrinsic viscosities and ABR is the difference in birefringence of the two components.

2. A filament according to claim 1, wherein the factor AlV-ABR lies in the range 2.9 10 to 4.5 10- 3. A filament according to claim 1, wherein the factor AIV-ABR lies in the range 1.4)(10 to 2.1X10- 4. A filamentary non-Woven structure comprising filaments according to claim 1, having a specific volume when uncompressed of at least cubic centimetres per gram and a specific volume when compressed under a load of 10 grams per square centimetre of at least 30 cubic centimetres per gram.

References Cited UNITED STATES PATENTS Moncrieft, R. W.: Man-Made Fibres, John Wiley and Sons, Inc., New York, 1966, pp. 63-64.

ROBERT F. BURNETT, Primary Examiner L. M. CARLIN, Assistant Examiner U.S. Cl. XJR. 

